London: British Prime Minister Theresa May, has stated that it was “highly likely” that Russia was responsible for the poison attack that left a former Russian double agent and his daughter comatose on a park bench last week.

Retired military intelligence officer Skripal, 66, and his daughter, Yulia, 33, were found slumped on a bench in Salisbury city centre on March 4.

They remain in a critical but stable condition in hospital.

In a strongly worded statement to the House of Commons May said the “military grade” nerve agent used in the attack had been identified as Novichok, a substance developed in the Soviet Union in the 1970s, reported CNN.

In a move that is likely to plunge the UK-Russia ties to a new low, The British Prime Minister has demanded a response from the Russian government by the end of Tuesday, making it clear “Should there be no credible response, we will conclude that this action amounts to an unlawful use of force by the Russian state against the United Kingdom.”

May added, “This attempted murder using a weapons-grade nerve agent in a British town was not just a crime against the Skripals. It was an indiscriminate and reckless act against the United Kingdom, putting the lives of innocent civilians at risk. And we will not tolerate such a brazen attempt to murder innocent civilians on our soil.”

Dismissing May’s comments Russian Foreign Ministry spokeswoman Maria Zakharova, told CNN, “This is a circus show in the British Parliament. The conclusion is obvious.”

The White House noted that the use of a highly lethal nerve agent against Skripal and his daughter “is an outrage,” adding that the attack was “reckless, indiscriminate and irresponsible.”

According to the reports, Skripal was convicted by the Russian government of passing secrets to UK’s Secret Intelligence Service MI6 in 2004, but was given refuge in the UK in 2010 as part of a “spy swap.”(ANI)